7. What are the risks posed by fluorides?

7.1 What are the risks to humans?

The source document for this Digest states:

Fluoride has both positive and negative effects on human health, but there is a narrow range between intakes that are associated with these effects. Exposure to all sources of fluoride, including drinking-water and foodstuffs, is important.

There is little information to characterize the dose–r esponse relationships for the different adverse effects. In particular, there are few data on total exposure, particularly with respect to intake and fluoride absorption.

The most serious effect is the skeletal accumulation of fluoride from long-term excessive exposure to fluoride and its effect on non-neoplastic bone disease — specifically, skeletal fluorosis and bone fractures. There is clear evidence from India and China that skeletal fluorosis and an increased risk of bone fractures occur at total intakes of 14 mg fluoride/day and evidence suggestive of an increased risk of bone effects at total intakes above about 6 mg fluoride/day.

7.2 What are the risks to the environment?

The source document for this Digest states:

In the freshwater environment, natural fluorideconcentrations are usually lower than those expected to cause toxicity in aquatic organisms. However, aquatic organisms might be adversely affected in the vicinity of anthropogenic discharges. Fluoride toxicity is dependent on water hardness.

Sensitive plant species growing near anthropogenic sources of fluoride are at risk. The release of fluoride from anthropogenic sources is associated with damage to local terrestrial plant communities, but it is often difficult to attribute these effects to fluoride alone, due to the presence of other atmospheric pollutants. Fluoride is generally strongly adsorbed by soils. Consequently, plant uptake via this pathway is relatively low, and leaching of fluoride through soil is minimal.

Concentrations of fluoride in vegetation in the vicinity of fluoride emission sources, such as aluminium smelters, can be higher than the lowest dietary effect concentration reported for mammals in laboratory experiments. Fluorosis in domesticated animals has been reported. There are still some areas reporting fluorosis incidents in livestock due to uptake of fluoride-rich mineral supplements and drinking-water. Furthermore, there is a potential risk from fluoride-contaminated pasture and soil ingestion due to the long-term use of phosphate fertilizers containing fluoride as an impurity. Fluoride-induced effects, such as lameness and tooth damage, have also been reported in wild mammals close to anthropogenic sources